In the past, for various apparatuses used in the process of manufacturing a liquid crystal display or the process of manufacturing a semiconductor, an aluminum alloy containing magnesium has been often used.
A surface of the various apparatuses is exposed to a strong corrosive gas such as a chlorine gas, a hydrogen fluoride gas, a fluorine radical, or the like. For the aluminum alloy used for the apparatuses, an alumite film has been formed on a surface thereof by an alumite treatment to improve a corrosion resistance and to archive a long-life thereof.
However, there was a problem that the alumite film is etched by the fluorine radical and then destroyed when the film is used for a long time.
A magnesium alloy oxidizes in the air on its own, a color of the surface thereof easily changes, and the magnesium alloy is also easily affected by salt damage.
In addition, for a surface treatment method for the aluminum alloy containing magnesium, there has been disclosed a method which includes the steps of heating an object in a container, introducing a dangerous fluorine-based gas or a fluorine-based compound gas into the container thereby heating the container, and forming a film made of a fluoride on the surface of the aluminum alloy containing magnesium (for example, refer to Japanese Unexamined Patent Application Publication No. 9-176772)